On Mon, 2012-01-30 at 11:14 +0100, Eric Dumazet wrote:
> Le lundi 30 janvier 2012 à 12:51 +0300, Denis Kirjanov a écrit :
> > I'll check this out. After kernel.org was cracked I've missed
> > @kernel.org mail account.
>
>
> At first glance, start_tx() is racy against TX completion.
>
> It does :
>
> if (np->cur_tx - np->dirty_tx < TX_QUEUE_LEN - 1 &&
> !netif_queue_stopped(dev)) {
> /* do nothing */
> } else {
> netif_stop_queue (dev);
> }
>
> So it can call netif_stop_queue() while TX completion handler did a
> cleanup of all queued packets right before.
Yes, I spotted that. But no descriptors are pushed to the hardware
here; that's done in the driver's TX tasklet. Although... maybe that
can run immediately when scheduled from here? I've never had to deal
with tasklets so I really don't know their semantics.
Ben.
> Note intr_handler() doesnt hold the queue spinlock when it does :
>
> if (netif_queue_stopped(dev) &&
> np->cur_tx - np->dirty_tx < TX_QUEUE_LEN - 4) {
> /* The ring is no longer full, clear busy flag. */
> netif_wake_queue (dev);
> }
>
>
>
--
Ben Hutchings
Lowery's Law:
If it jams, force it. If it breaks, it needed replacing anyway.
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